One type of conventional prune pitting apparatus is described in U.S. Pat. No. 3,556,281, issued Jan. 19, 1971. FIG. 1 is a simplified side elevational view (partially cut away) of such an apparatus. FIG. 2 is a cross-sectional view of the FIG. 1 apparatus taken along line 2--2 of FIG. 1. The pitting apparatus of FIG. 1 includes a frame (with sideplates 12, legs 17, and pitting head housing 22), pulley and sprocket assembly 32, sprocket assembly 32D, disks 34, and two conveyor chains 35 looped around sprocket assemblies 32 and 32D and disks 34. Each of assemblies 32 and 32D is rotatably mounted to the frame. The drive mechanism comprises motor 24, speed reducer 26, pulley 23 (attached to a first shaft mounted for rotation relative to housing 22), pulleys 21A and 21B (attached to a second shaft mounted for rotation relative to housing 22), drive belt 28 looped around pulleys 23 and 21A, and drive belt 30 looped around pulley 21B and a pulley of assembly 32. In operation, motor 24 and speed reducer 26 cause pulley 23 to rotate clockwise (in FIG. 1), thus causing belt 28 to rotate both pulleys 21A and 21B clockwise and causing belt 30 to rotate assembly 32 clockwise. Rotating assembly 32 drives each of the conveyor chains 35 clockwise around a loop defined by sprocket assemblies 32 and 32D and disks 34. One of the chain loops is in the plane of FIG. 1, and the other chain loop is in a vertical plane parallel to the plane of FIG. 1. More specifically, as shown in FIG. 4, pulley and sprocket assembly 32 includes pulley 32B and sprockets 32C, all connected to shaft 32A. As belt 30 rotates pulley 32B, pulley 32B in turn rotates shaft 32A and sprockets 32C together as a unit, thereby driving chains 35 (each chain 35 being looped around one of sprockets 32C).
Fruit holders 36 (shown in FIG. 2) are connected between conveyor chains 35, so that the fruit holders 36 are conveyed around the loop as chains 35 are driven. A roller carrier 54 is attached at one end of each holder 36, and a roller carrier 56 is attached at the holder's other end. A roller 66 is attached to each carrier 54, and a roller 68 is attached to each carrier 56. Each fruit holder includes four pocket members 58 and four pocket members 60, which define four adjustable pockets (each pocket being dimensioned to hold firmly one of the prunes or other articles to be pitted when the pocket is in a closed configuration). Variable-length rods 50 extend between carriers 54 and 56, and a spring 62 is provided between holder 36 and each of carriers 54 and 56 to spring-load the rods into their maximum-length configuration (in which members 58 and 60 are oriented so as to hold the pockets in an open configuration). Members 58 and 60 are pivotably mounted to rods 50 so that when rods 50 are compressed by action of cams 84 (mounted along sideplates 12) on rollers 66 and 68, the members 58 and 60 pivot to decrease the size of (i.e., close) the pockets. When cams 80 allow springs 62 to move rods 50 to their elongated configuration, members 58 and 60 pivot in the opposite direction to increase the size of (i.e., open) the pockets.
FIG. 3 is a cross-sectional view of the FIG. 2 apparatus (with roller 68 omitted for clarity), taken along line 3--3 of FIG. 2, showing one of paddle wheels 38 sweeping across the pockets of a fruit holder 36. As shown in FIGS. 2 and 3, cams 80 are separated by a relative large distance, so that the pockets defined by fruit holders 36 are open when holders 36 translate past cams 80. As shown in FIG. 2, cams 84 are separated by a smaller distance so that the pockets defined by holders 36 are closed when holders 36 translate past cams 84. A third pair of cams (cams 85 and 85A, shown in FIGS. 4 and 5 but not in FIGS. 1 or 2) is also mounted to sideplates 12A in pitting head housing 22 to perform pocket opening and closing functions (to be described below) within housing 22. A fourth pair of cams (cam bars 111, one of which is shown in FIG. 1) is also mounted to side plates 12A between paddle wheels 38 and pitting head housing 22 to perform pocket opening and closing functions (to be described below). Cams 80 are mounted in positions in which they cause the pockets to open when holders 36 translate past hopper 14 (to allow the pockets to receive prunes or other articles). Cams 84 are mounted in positions in which they cause the pockets to close when holders 36 translate past paddle wheels 38. Cams 85 and 85A are mounted in positions in which they cause the pockets to close as holders 36 approach pitting knives within housing 22, and then to open briefly immediately after the pit removal operation (while the pitting knives remain engaged with the fruit in holders 36), and then to close again as holders 36 continue to move through housing 22 after the pit removal operation.
Typically, cams 80 are attached to the frame by adjustable mounts 82 so that the distance between cams 80 can be adjusted when desired (e.g., between processing of a batch of prunes of one average size and processing of another batch of prunes of a different average size). Similarly, cams 84 are attached to the frame by adjustable mounts 86, and cams 85 and 85A are attached to the frame by adjustable mounts 37 (shown in FIG. 4), so that the distance between cams 84 and between cams 85 and 85A can be adjusted when desired (e.g., in the same circumstances in which mounts 82 are adjusted).
Hopper 14 (having sideplates 16 and endwall 10) of the FIG. 1 apparatus is positioned so that the prunes, dates, or similar soft fruit to be pitted (e.g., prunes P shown in FIGS. 1 and 2) drop onto holders 36 as the holders pass under hopper 14. The FIG. 1 apparatus also includes hood 20 (which is supported above the upper end of hopper 14 and typically houses a water spray system for spraying water on the fruit translating past it) and paddle wheels 38. Paddle wheels 38 are rotatably mounted within hood 20, and are typically driven (by means not shown) to rotate sufficiently rapidly about their central axes (which are perpendicular to the plane of FIG. 1) so that the paddles of each wheel 38 sweep several times across each holder 36 as the holders 36 translate past the wheels 38. As indicated in FIG. 3, each time one of the paddles of wheel 38 sweeps across the pockets of a holder 36, protruding portions 78 of the paddle sweep through corresponding recesses 76 of the holder 36. Thus, paddle wheels 38 sweep out of the pockets any prunes (or other articles) that are not firmly seated (typically in a vertical orientation) between a pair of pocket members 58 and 60.
Each holder 36 has a lower plate 46 in which a pitting cup 70 is mounted at the location of each pocket (holder 36 shown in FIG. 3 has four cups 70, one at the location of each pocket). Pitting cups 70 are sometimes referred to as pitting rubbers, since they are typically made of rubber. Each cup 70 has a pit ejection opening 72 extending through it. Each holder 36 also has an upper plate 44 with a funnel-shaped opening 74 at the location of each pocket (for guiding an article into the pocket so as to rest on cup 70 between members 58 and 60). As shown in FIG. 3, one of conveyor chains 35 is attached to one side of plate 46 of each holder 36, and the other of chains 35 is attached to the other side of such plate 46.
In operation, prunes P (or dates or other articles to be pitted) fall from hopper 14 onto cups 70, as the conveyor translates holders 36 past the hopper, so that a prune (or other article) is loaded into each of at least some of the pockets defined by holders 36. The prunes (within holders 36) then translate past paddle wheels 38, and then through cam assembly 111 (shown schematically in FIG. 1). Assembly 111 comprises a pair of cam tracks 111A and 111B (also referred to herein as shaker bars), best shown in FIG. 2A.
Shaker bars 111A and 111B are cam tracks similar to above-described cam tracks 84, but each of bars 11A and 111B has periodically varying width and thus defines a scalloped (or other periodically varying) cam surface, whereas each cam 84 has uniform width (away from its ends) and thus defines a straight cam surface. Shaker bars 111A and 111B are mounted to sideplates 12 in positions in which they cause the pockets of each holder 36 to open and close rapidly and periodically as holders 36 translate past the shaker bars (i.e., as roller 66 of each holder 36 follows the cam surface of bar 111A and roller 68 of each holder 36 follows the cam surface of bar 111B). This periodic opening and closing of the pockets causes the articles to be pitted to settle completely into the pockets.
Assembly 111 also includes means for adjustably attaching shaker bars 111A and 111B to sideplates 12 of the frame. For example, adjustable mounts 186 (shown in FIG. 2A) can be provided, so that the distance between bars 111A and 111B can be adjusted when desired (e.g., in the same circumstances, described above, in which mounts 82 are adjusted to vary the spacing of cams 80). Alternatively, each of bars 111A and 111B is mounted to a plate (or angled bracket), and each plate (or bracket) has slots for receiving bolts for mounting the bar to the plate (bracket) and the plate (bracket) to the frame. When the bolts are loosened, each plate (bracket) can be repositioned relative to the frame (so that the slots translate relative to the bolts) and then fixed in the new position by re-tightening the bolts.
With reference again to FIG. 1, after holders 36 (and the prunes or other articles carried in their pockets) have translated past shaker bars 111 and into housing 22, a reciprocating pitting knife assembly in housing 22 engages the translating prunes (or other articles) to push out the pit from within each prune.
The pits either fall directly into chute 83 (shown in FIG. 4), or they are brushed away from the holders by a rotating brush assembly (to be described with reference to FIG. 4) and then fall into chute 83. The rotating brush assembly comprises rotatably mounted pit brush 61 (having paddles tipped with rubber), brush drive sprocket 59, brush drive shaft 63 (to which sprocket 59 is attached), and brush drive chain 64 looped around sprocket 59 and shaft 63. Sprocket 59 and above-described pulleys 21A and 21B are mounted to the same rotatable shaft. In response to rotation of sprocket 59 (with pulleys 21A and 21B) by motor 24, chain 64 rotates shaft 63, thereby actively rotating brush 61 relative to each of holders 36 translating away from the pitting knives so that the paddles of brush 61 sweep away any pits that may cling to the holders (so that the pits fall into pit chute 83).
Following pitting, as the holders exit the pitting head, the pockets defined by each holder are opened by cam assembly 216 (comprising a pair of pocket-opening cam tracks similar to above-described cam tracks 80) shown schematically in FIG. 1, and the pockets are then shaken by passing through shaker bar assembly 213 (comprising shaker bars similar to above-described bars 111A and 111B), to cause the pitted prunes fall out of the pockets.
The pitting knife assembly typically includes multiple rows of pitting knives (one row of knives for pitting fruit in each of two or more holders 36). Each row of pitting knives includes one knife for each pocket defined by one of the holders (e.g., one knife for each of the four pockets defined by holder 36). For example, in the apparatus of FIGS. 2-9 there are two rows of pitting knives, each row comprising four knives 102. The knives 102 in one row pit the prunes in one holder 36 while the knives in the other row simultaneously pits the prunes in another holder 36 (so that a total of eight prunes can simultaneously be pitted). A conventional implementation of such a knife assembly will be described with reference to FIGS. 4-8.
This conventional pitting knife assembly includes two shafts 4 which are fixedly mounted between vertically oriented plates 12A of housing 22 (as shown in FIGS. 7 and 8). A portion of the knife assembly of FIGS. 4-8 hangs from shafts 4 (in a manner to be explained below).
The knife assembly also includes rotatably mounted drive shaft 21, which is rotated about its axis by belt 28, which is in turn driven by motor 24. Cam 9 and eccentric 42 are fixedly mounted to shaft 21 (at different locations along the axis of shaft 21). To mount cam 9 to shaft 21, a channel (not shown) through cam 9 is aligned with an orifice (not shown) in shaft 21, and key 41' is inserted through the channel and tightened into the orifice.
Eccentric 42 is attached to eccentric shaft member 114, with eccentric 42 having freedom to rotate relative to member 114. As shaft 21 rotates about its longitudinal axis, eccentric 42 (which rotates as a unit with shaft 21) exerts force on member 114 which causes member 114 to undergo reciprocating motion as follows: the center of gravity of member 114 translates back and forth along an arc of a circle in the plane of FIG. 8, but member 114 does not rotate (about its center of gravity) in the plane of FIG. 8.
Member 114 is fixedly attached to a carriage comprising upper carriage plate 7, lower carriage plate 132, tie bar 30, and a pair of tie bars 8 (only one of bars 8 is shown in FIG. 7).
The carriage hangs from a pair of rotatably mounted swing arms 2. The upper end of each arm 2 is rotatably attached to one of parallel shafts 4. A pin 119 protrudes from the lower end of each arm 2 into a tube 120. Both tubes 120 are fixedly attached to lower carriage plate 132. Thus, as the carriage rocks back and forth (in response to rotation of eccentric 42), the carriage imparts this rocking motion to tubes 120 and pins 119, thus causing arms 2 to swing back and forth on fixed shafts 4. More specifically, as the carriage rocks, pins 119 translate reciprocally as a unit with tubes 120. During the reciprocal translation of pins 119 together with tubes 120, each pin 119 rotates relative to the tube 120 which surrounds it (about the common axis of the pin and the surrounding tube).
Two parallel plunger shafts 15 extend through upper carriage plate 7 and lower carriage plate 132, each with freedom to translate in the direction of its longitudinal axis relative to the plates 7 and 132. A pitting knife assembly (including four rows of pitting knives 102) is fixedly attached to the lower ends of shafts 15. Thus (assuming for the moment that shafts 15 are held fixed relative to the carriage), as the carriage (including plates 7 and 132) rocks back and forth, shafts 15 translate reciprocally as follows: the center of gravity of each shaft 15 translates back and forth along an arc of a circle in the plane of FIG. 8, but neither shaft 15 rotates (about its center of gravity) in the plane of FIG. 8.
However, the actual motion of shafts 15 (and the knives 102 fixedly attached thereto) is more complicated, because a mechanism (including cam 9 and rocker arm unit 33) provided to reciprocate shafts longitudinally relative to the carriage as the carriage rocks back and forth. Unit 33 includes top rocker arms 18, rocker spacer 19, bottom rocker arms 20, and rocker arm body 38, to be described below). The longitudinal motion of shafts 15 is timed relative to the swinging motion thereof (by the orientation of cam 9 relative to that of eccentric 42), so that the knives 102 undergo the following motion: knives 102 move longitudinally downward (into engagement with the prunes to be pitted) while the carriage swings in the direction of motion of the prunes (which corresponds to "toward the right" in FIG. 8), knives 102 then move longitudinally upward (until they are out of engagement with the prunes) while the carriage continues to swing in the direction of motion of the prunes, knives 102 then continue to move longitudinally upward while the carriage begins to swing in opposite direction (toward the left in FIG. 8), and finally knives 102 begin to move longitudinally downward (toward a new set of prunes to be pitted) while the carriage continues to swing in the direction opposite the direction of motion of the prunes.
Each knife 102 preferably has a groove 102A (a small diameter portion) near its tip (as shown in FIGS. 7 and 17). Each groove 102A defines shoulders which engage the fruit flesh when the knife is being withdrawn after pitting (to assist in separating the pitted fruit from the holder).
Next, with reference to FIGS. 5, 6, and 9, we describe the pitting operation in more detail (in an implementation in which motor 24 continuously translates holders 36 around the loop defined by sprocket assemblies 32 and 34). FIG. 5 shows a holder 36 and one row of four knives 102 in their lowest position (extending all the way through pitting rubbers 70 of the four pockets defined by the holder), in the position the knives would occupy immediately after pushing pits downward (through rubbers 70) from within four articles of fruit seated in the pockets. FIG. 6 shows one knife 102 of each of the two rows of knives 102, also in the lowest knife position. For clarity, portions of some of the holders 36 mounted on chains 35 are not shown in FIG. 6 (only the pitting rubbers 70 of the partially-shown holders 36 are visible in FIG. 6).
As shown in FIGS. 5 and 6, fruit stripping grill 94 is mounted (by brackets 94A) between plates 12A. After the pitting operation, as knives 102 move upward and to the right (when viewed as in FIG. 6) relative to fixedly mounted grill 34, the grill strips the pitted fruit from the knives. The pitting knives 102 then move back to the left (when viewed as in FIG. 6) away from grill 94. The holders (with pitted fruit) then translate to cam assembly 216 (which opens the spring-biased pockets of each holder) and then to cam assembly 213 (which shakes the pitted fruit from the pockets) so that the pitted fruit fall from the holders into a product bin or conveyor (not shown). Optionally, water is sprayed on the pitted fruit and on grill 94 (e.g., from spray pipe 37 and spray nozzle 48 shown in FIG. 4).
In the plane of FIG. 5 (corresponding to plane "A" of FIG. 9), cam tracks 85 and 85A (each mounted to one of plates 12A of housing 22 as shown in FIG. 5) are separated by a relative small distance, so that the pockets defined by holders 36 are closed to grip tightly the fruit being pitted. After the pitting step, each holder 36 of FIGS. 5 and 6 continues to translate (out of the plane of FIG. 5; toward the right in FIG. 6) until the holder (e.g., the holder 36 shown in FIG. 5) encounters notches 85B (best shown in FIG. 9) in cam tracks 85 and 85A. While each holder 36 translates between notches 85B, the holder's springs (springs 62, described with reference to FIG. 3) briefly relax and are then recompressed (thereby briefly opening the pockets). Knives 102 (which extend through the fruit in each pocket of the holder at the end of the pitting step) begin to translate upward while the pockets are briefly open. The brief opening of each pocket (in response to relaxation of the springs) releases pressure on the pitted fruit in each pocket, thereby allowing upward-translating knives 102 to strip the fruit from pitting rubbers 70 of the pockets before the pockets return to their closed configuration. This action improves the efficiency of separation of the pitted fruit from the holders (by assemblies 216 and 213) following pitting.
As noted, each of cam tracks 85 and 85A has a notch 85B. The cam tracks are mounted so that each holder 36 translates between input ends 89 of tracks 85 and 85A (shown in FIG. 9) before the pitting step, and then translates between notches 85B after the pitting step. Since there are two rows of pitting knives 102 which simultaneously pit fruit in two holders 36, one holder of each such pair of holders translates between the notches 85B immediately after the pitting step, and the second holder of each pair translates between notches 85B only after the first holder has done so. Typically, roller 66 at one end of each holder 36 is offset (in the direction in which holder 36 translates) from roller 68 at the other end of the holder 36. The notches 85B have length such that when rollers 66 and 68 of one holder 36 of a pair of adjacent holders are in plane A (indicated in FIG. 9), rollers 66 and 68 of the other holder 36 of the pair are in plane C of FIG. 9, and when rollers 66 and 68 of one holder 36 of the pair are in plane B of FIG. 9 (i.e., when the holder is between aligned notches 85B), rollers 66 and 68 of the other holder 36 of the pair are in plane D of FIG. 9 (i.e., the holder is between the aligned tapered ends of cam tracks 85 and 85A). Thus, just after knives 102 have pitted the fruit articles in a pair of adjacent holders 36 and at an instant when the knives 102 begin to move upward (away from the pitting rubbers 70), one of the holders (the "second" holder) is positioned in plane B of FIG. 9 (between notches 85B) with its pockets opened, and the other holder in the pair (the "first" holder) is positioned in plane D of FIG. 9 with its pockets also opened. Just before this moment, the rollers of the first holder had reached plane C of FIG. 9 where the first holder's pockets were held closed by tracks 85 and 85A (while pitting knives 102 moved downward into engagement with the fruit articles in the first holder to pit such fruit articles), while the rollers of the second holder reached plane A of FIG. 9 where the second holder's pockets were also held closed by tracks 85 and 85A (while the other row of pitting knives 102 moved downward into engagement with the fruit articles in the second holder to pit such fruit articles). More generally, as each pair of adjacent holders 36 translates along their looped path, the pockets of both holders are simultaneously closed (to perform the pitting operation), and then simultaneously opened (for a brief time while the knives begin to retract), and then simultaneously closed again (while the knives 102 continue to retract upward). Then, when the knives 102 have retracted sufficiently far upward so that their tips approach grill 94, the pockets open again (as the rollers of both holders have translated, toward the right in FIG. 9, beyond plane D) so that grill 94 can strip from knives 102 any pitted fruit that clings to the knives. Of course, the pockets should be open during the stripping step, so as not to reduce the efficiency with which the retracting knives separate from the pitted fruit.
In variations on the described embodiment in which rollers 66 and 68 of each holder 36 are aligned, cam tracks 85 and 85A should be mounted so that notches 85B are also aligned (so that planes A, B, C, and D of FIG. 9 would extend vertically, rather than at an angle from vertical as shown in FIG. 9).
Next, with reference again to FIGS. 7 and 8, we describe the manner in which cam 9 and rocker arm unit 33 cause shafts 15 to execute longitudinally reciprocating motion, thereby cyclically raising and lowering the pitting knives 102 attached to the lower ends of shafts 15. As best shown in FIG. 8, top rocker arm 18 and bottom rocker arm 20 of unit 33 are attached to each other at one end of unit 33 by rocker spacer 19 and at the other end of unit 33 by rocker arm body 38. One end of body 38 of unit 33 (comprising pin 112 shown in FIG. 8) is pivotally attached to stroke adjustment bearing screw 110 and stroke adjustment support bar 11. Element 110 is adjustably attached to support bar 11, and bar 11 is fixedly attached to one of frame plates 12A. With element 110 fastened in a selected position relative to bar 11, unit 33 is free to pivot reciprocally (both clockwise and counterclockwise in the plane of FIG. 8) about pin 112 in response to the forces alternately exerted thereon by rotating cam 9 and shafts 15 (which are spring-loaded as described below). Before operating the apparatus, screw 110 can be repositioned relative to bar 11 in order to change the position of pin 112 and unit 33 (and thus shafts 15 engaged with unit 33) relative to the frame of the apparatus during operation.
A cam follower 140 is attached to unit 33 between the fixed end of unit 33 (the end attached to pin 112) and the free end of unit 33 (the left end in FIG. 8). A cam follower 23 protrudes from each of shafts 15 into engagement with unit 33 (near unit 33's free end), so that when unit 33 pivots clockwise in FIG. 8, unit 33 pulls cam followers 23 upward (and thus unit 33 pulls shafts 15 longitudinally upward). Shafts 15 are spring-loaded by compressing two identical springs 126 between carriage plate 132 and spring centering members 129 (one member 129 is fixedly attached to each of shafts 15). The lower end of each spring 126 is held in position by a centering plug portion of plate 132.
The outer surface (cam surface) of cam 9 engages cam follower 140. When the large radius portion of cam 9 (the portion of cam 9 having greatest radial thickness relative to the central longitudinal axis of shaft 21) rotates into engagement with cam follower 140, cam 9 pushes follower 140 down, thus pivoting the arm unit 33 counterclockwise about pin 112, which causes arm unit 33 to pull cam followers 23 downward, which in turn translates shafts 15 longitudinally downward relative to the carriage. As shafts 15 translate longitudinally downward relative to the carriage, spring centering members 129 move downward (with shafts 15) relative to the carriage, thereby compressing springs 126.
Then, when continuing rotation of shaft 21 rotates the small radius portion of cam 9 (the portion of cam 9 having less radial thickness than does the large radius portion) into engagement with cam follower 140, compressed springs 126 relax (their length increases), thus pushing members 129 upward and causing shafts 15 to translate longitudinally upward relative to the carriage. As shafts 15 translate longitudinally upward relative to the carriage, cam followers 23 pivot arm unit 33 clockwise about pin 112. This pivoting motion of arm unit 33 pushes cam follower 140 upward so that cam follower 140 remains in contact with cam 9.
However, the conventional knife assembly described above has several limitations and disadvantages, including the following:
the knife assembly is undesirably spring-loaded (by compressing springs 126 between members 129 and carriage plate 132), and must remain spring-loaded in operation (which increases power consumption, which increases the cycle time of the periodic motion of shafts 15 and necessitates replacement of springs 126 from time to time as they wear out); PA1 when motor 24 is turned off (after the knife assembly has been operating in response to rotation of shaft 21 by motor 24), springs 126 rapidly relax, thus driving shafts 15 longitudinally upward suddenly (this sudden action is potentially dangerous to workers in the vicinity of the apparatus, and increases wear and tear on the motor and other components of the apparatus, which in turn shortens the lifetime of the motor and other components); PA1 when motor 24 is turned off, springs 126 rapidly pull driving shafts 15 longitudinally upward and hold shafts 15 (and the pitting knives attached thereto) in their fully raised position (this is inconvenient since the operator or service technician will sometimes prefer that the knives remain in a lowered position when the motor is turned off); and PA1 the pitting knife assembly's set up process is difficult in the sense that, not only must springs 126 be installed and compressed, but the proper relative orientation of cam 9 and eccentric 42 must be set to ensure that shafts 15 move longitudinally up and down in proper synchronization with the rocking motion of the carriage (typically two persons are needed to set up the apparatus); PA1 the set up process of the apparatus is also difficult since actively rotating pit brush 61 must be appropriately oriented and its rotation appropriately timed (to avoid collisions between fruit holders 36 and paddles of brush 61 during operation); and PA1 actively rotating pit brush 61 is an expensive assembly that requires maintenance (including periodic replacement of its paddles).
Some conventional variations on the above-described pitting apparatus employ an intermittent fruit holder conveyor drive mechanism. In such variations, the fruit holders are translated into position for pitting, then remain stationary during pitting, and are then translated away from the pitting position. However, conventional pitting apparatus employing such an intermittent conveyor-drive have not efficiently separated the pitted fruit flesh (and pits) from the holders after pitting. An important factor contributing to this problem is that because the fruit is gripped tightly to accomplish the pitting operation, there is substantial friction between the pitting knife, fruit holder, and the fruit flesh both during the downward (pitting) stroke of each knife and the upward (retracting) knife stroke which follows the pitting stroke.
It had not been known until the present invention how to design an apparatus for pitting prunes or dates (or similar soft fruit) in a manner overcoming the disadvantages and limitations of the described conventional pitting apparatus.
It has been proposed to use a box cam in a pitting knife drive assembly See U.S. Pat. No. 5,619,912, issued Apr. 15, 1997 and assigned to the assignee of the present invention. However it has not been proposed to use a box cam in an apparatus for pitting prunes or dates (or similar soft fruit), in which the fruit is carried in holders having fruit-receiving pockets of controllable size, where each pocket must be opened and closed at different times during the processing cycle to grip and free the fruit sequentially in order to accomplish pitting efficiently. It had not been appreciated until the present invention that the efficiency of pitting of prunes, dates, and similar soft fruit can be significantly increased (with less waste due to fruit flesh and/or pits clinging to the fruit holders and fruit flesh being discarded with the ejected pits) if the pitting knives are driven using a box cam, and can be increased even more by driving the pitting knives using a box cam and also controlling the holder pockets to open briefly and then reclose following pitting (while the knives remain engaged with the pitted fruit).